TCP STATE DIGRAM

TCP FORMAT

TCP: The Connection-Oriented Transport Protocol

TCP important features that worth mentioning:

• Stream-oriented processing— TCP processes data in a stream. In other words, TCP can accept data a byte at a time rather than as a preformatted block. TCP formats the data into variable-length segments, which it will pass to the Internet layer.

• Resequencing— If data arrives at the destination out of order, the TCP module is capable of resequencing the data to restore the original order.

• Flow control — TCP's flow control feature ensures that the data transmission won't outrun or overrun the destination machine's capability to receive the data. This is especially critical in a diverse environment in which there may be considerable variation of processor speeds and buffer sizes.

• Precedence and security— The Department of Defense specifications for TCP call for optional security and priority levels that can be set for TCP connections. Many TCP implementations, however, do not provide these security and priority features.

• Graceful close— TCP is as careful about closing a connection as it is about opening a connection. The graceful close feature ensures that all segments have been sent and received before a connection is closed.

Well-Known UDP Ports

Service	UDP Port Number	Description
echo	7	Echo
discard	9	Discard or null
systat	11	Users
daytime	13	Daytime
netstat	15	Network status
qotd	17	Quote of the Day
chargen	19	Character generator
time	37	Time server
name	42	Host Name server
domain	53	Domain name server (DNS)
nameserver	53	Domain name server (DNS)
bootps	67	Bootstrap protocol service/DHCP
bootpc	68	Bootstrap protocol client/DHCP
tftp	69	Trivial File Transfer Protocol
portmap	111
sunrpc	111	SUN RPC service
ntp	123	Network Time Protocol
nbname	137	NetBIOS name
nbdatagram	148	NetBIOS datagram
sgmp	153
snmp	161	Simple Network Management Protocol
snmp-trap	162	Simple Network Management Protocol trap

Well-Known TCP Ports

Service	TCP Port Number	Brief Description
tcpmux	1	TCP port service multiplexor
compressnet	2	Management utility
compressnet	3	Compression utility
echo	7	Echo
discard	9	Discard or null
systat	11	Users
daytime	13	Daytime
netstat	15	Network status
qotd	17	Quote of the Day
chargen	19	Character generator
ftp-data	20	File Transfer Protocol data
ftp	21	File Transfer Protocol control
telnet	23	Terminal network connection
smtp	25	Simple Mail Transport Protocol
nsw-fe	27	NSW user system
time	37	Time server
name	42	Host name server
domain	53	Domain name server (DNS)
nameserver	53	Domain name server (DNS)
DHCP	67	Dynamic Host Configuration Protocol
gopher	70	Gopher service
rje	77	Remote job entry
finger	79	Finger
http	80	WWW service
link	87	TTY link
supdup	95	SUPDUP protocol
hostnames	101	sri-nic host name server
iso-tsap	102	ISO-TSAP
x400	103	X.400 mail service
x400-snd	104	X.400 mail send
pop	109	Post Office Protocol
pop2	109	Post Office Protocol 2
pop3	110	Post Office Protocol 3
portmap	111
sunrpc	111	SUN RPC service
auth	113	Authentication service
sftp	115	Secure FTP
path	117	UUCP path service
uucp-path	117	UUCP path service
nntp	119	Usenet Network News Transfer Protocol
nbsession	139	NetBIOS session service
NeWS	144	News
tcprepo	158	TCP repository